The present invention is related to logging carriages and more particularly to such carriages used in conjunction with highline type logging for the purpose of skidding logs from a hillside to a landing.
"Highline" or "skyline" type logging is used primarily in steep forested country where conventional wheel or track type skidders cannot be effectively utilized. In this type of logging operation, a landing or flat area is located along a roadbed adjacent the area to be logged. A "yarder" (a specially built crane with two or more fairload lines and winch arrangements) is positioned at the landing. The "highline" extends from the top fairlead of the yarder up or down the hillside to an anchor point. A carriage is then movably mounted to the highline to carry a "mainline" up or down the hillside. Cut logs are gathered on choker cables at the free end of the mainline and are pulled to the carriage by the mainline winch.
The typical carriage includes some form of internal mechanism that alternately clamps the carriage to either the skyline or the mainline. The mechanism is used to clamp the carriage to the mainline while it is moving along the skyline from the yarder along the hillside toward the anchor point and back along the hillside with a "turn" of logs. As the carriage reaches a desired destination, it becomes desirable to release the mainline and clamp the carriage to the highline. This is typically accomplished by some form of actuator mechanism on the highline, set at a location adjacent the cut logs. The actuator causes an internal mechanism to grip the skyline, halting further progress of the carriage, and to release the mainline. The mainline can then be pulled from the carriage to the cut logs where the chokers can be connected. The mainline winch is then operated to pull the mainline back through the carriage and toward the yarder. This brings the log or logs through the carriage, which is clamped in a stationary position on the skyline.
As the log or logs arrive at the carriage, an actuator along the mainline trips the mechanism, releasing the highline clamps and, in some apparatus, sets a clamp against the mainline. The log or logs are then pulled over the hillside to the landing.
The highline is lowered with the mainline being held taut in order to lower the entire carriage and logs to the ground surface. The logs are then disconnected from the mainline and the highline is retightened to allow movement of the carriage along the hillside for the next successive load.
The difficulty with known forms of highline log carriages, is that the actuator along the highline must be manually placed along the length of the highline for the purpose of halting further progression of the carriage. This can be a difficult and hazardous duty, especially when the highline is suspended high above the ground. Furthermore, the abrupt shock of the carriage hitting the actuator produces severe strain on the highline causing premature wear and frequent breakage.
An additional problem is encountered at the landing, where the highline must be lowered in order to deliver the logs from the mainline, since there is no known form of actuator that may be situated adjacent the yarder along the highline for the purpose of releasing the mainline clamp and allowing the log or logs to drop onto the landing. Instead, the highline must be again handled to lower the carriage onto the landing. It is not desirable to continually change the tension and elevation of the highline during operation. It can easily become tangled in trees or undergrowth at any point along its length, requiring valuable time to untangle and free the highline for the next journey of the carriage over the hillside.
U.S. Pat. No. 1,543,473 to G. J. Fayette discloses a skyline logging carriage lock assembly operating on the same basic principles as described above. An abutment is situated along the skyline for the purpose of tripping a locking mechanism which releases the mainline.
The E. O Naud U.S. Pat. No. 3,079,008 discloses an electronically operated hoisting and conveying apparatus. The apparatus is basically a highline type logging carriage having a number of "radio controlled" braking mechanisms utilized for the purpose of halting progress of the carriage along the hillside and for clamping and releasing a mainline.
The M. J. McIntyre U.S. Pat. No. 3,083,839 discloses a cable logging operation that also makes use of radio control devices for actuating highline and mainline braking apparatus.
U.S. Pat. No. 2,649,209 to J. S. Wilson discloses a movable skyline terminal having actuators at opposite ends of a skyline that serve to cause alternate releasing and locking of the mainline. A ball on the mainline serves as a locking member against which a locking mechanism operates.
U.S. Pat. No. 3,948,398 to Donald D. Christensen discloses a self-locking logging skidding carriage with a simplified form of the skyline actuator mechanism. The actuator on the skyline serves to release the mainline at a selected position on the skyline, allowing it to be pulled out and connected to a turn of logs. Retraction of the mainline moves an actuator ball into engagement with the mechanism, causing it to unlock the skyline actuator and lock against the mainline to allow the mainline winch to pull the carriage and turn of logs along the hillside to the landing.
U.S. Pat. No. 1,509,716 to William G. Daniel is directed to a log carrier that utilizes several lines beyond the usual highline and mainline. Daniel supports his carriage on a single skyline but has several major and minor lines arranged on various pulleys for the purpose of pulling logs to the carriage, moving the carriage along the highline, and playing out the main, log engaging lines. The primary or major pull cable is extended, once the carriage is moved to a selected position, by drawing a secondary line over a pulley. The pulley turns and forces a second pulley to engage and rotate a grooved pulley that receives the primary pull cable. Taking up the secondary pulling line will cause the primary line to be drawn out from the carriage and allow attachment of logs to the free end thereof. Subsequently, retraction of the primary cable will pull the logs to the carriage. The carriage can then be moved along the highline to a landing.
Of the above patents and of all prior carriages known to the invention, none make use of a carriage operated solely from the mainline that include the functions of simultaneously gripping one line and releasing the other in response to engagement of an abutment on the mainline and in response to tension applied along the mainline.